Before World War II, when the U.S. Navy strung the first pipe down the highway, Key Westers had but one source for their water: rain. Even the aboriginal inhabitants, the Caloosa Indians, looked to the sky for replenishment of the island's natural wells. Dependent as they were on an unpredictable and sometimes stinting water god, the native Conchs learned early on how to catch and conserve rainwater. Not long after the island's first permanent settlers arrived in the 1820s were they building cisterns of every size and description, no doubt because their wells were being sucked into brackishness by the increased demand. Our old house on Fleming Street had one--we found it buried in the backyard while digging for the new pool. Old habits seem to die hard: Despite the unlimited availability of water piped in from the mainland, today's residents of the Keys use less water per capita than the rest of Florida. In our research for a recent television segment about the use of cisterns on the island, we were steered towards Merili McCoy, who grew up in Key West and is now one of the city's commissioners. Raised in the lighthouse keeper's quarters on Whitehead Street (her father was the head Coast Guardsman for the island), she learned early on the ways of water conservation, as she and her three brothers had to share one tub of water per bath--direct from the cistern on the grounds. "I was the only girl and the oldest, so I got in first," she recalls. Merili is a woman with a mission: She seeks government grants to resurrect the cistern as a means to solve a couple of problems at once. For one, collected rainwater is ideal for irrigation--why pour potable water, at $5.20 per thousand gallons, out on the monkey palm? Some estimates claim irrigation accounts for nearly 40% of water use in Key West, so easing that load would leave a large proportion of the 14 million gallons of piped-in water the island uses each day back in the Everglades aquifer where it belongs. Another benefit: Cisterns catch water that would otherwise become storm-water run-off--rain that falls, washes the island's building, streets and parking lots, and then needs a place to go. Currently, most of that greasy, dirty water ends up in the ocean, where it is implicated in killing off the living reef that surrounds the Keys. Although many were destroyed as anachronistic and breeders of mosquitoes after the Navy's pipe came in, there are still 353 cisterns of record on the island. Old Henry Flagler, builder of the railway that linked Key West to the mainland, put a million-gallon one beneath his Casa Marina Hotel back in 1922, and it's still being used to water the grounds. Good enough for Conchs and capitalists, the cistern seems to be an old idea that's coming back.